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    SKINthe human integument

    Dr. Zairuddin BinAbdullah Zawawi

    Pakar Ortopedik

    HRPZ II

    Kota Bharu,Kelantan

    http://ovidsp.tx.ovid.com/mms/434f4e1a73d37e8cabd934ac87c62ccfbb26022e918cd27ce52bf545de4e9e8706c09ae79783950c0cd9240f48257a18b437/8b3ffb8797137873efcfd1d66b29906118bade8f6110f2d82300189784fcf5033c38ffa7c442f64ff5779dba33f5df31f625/2df1f603ce2f857d962c238a9f9de1e03d528a45280b658918c9a7236dcc885f8076ffecccf12a985af2662623f0523a8f348f00ba74a3b3e30ecdb77c4ff786243dea1228ce47d2641a68b44a48d9f2e875e1bb588812c797877d03/FFU1.pnghttp://ovidsp.tx.ovid.com/mms/434f4e1a73d37e8cabd934ac87c62ccfbb26022e918cd27ce52bf545de4e9e8706c09ae79783950c0cd9240f48257a18b437/8b3ffb8797137873efcfd1d66b29906118bade8f6110f2d82300189784fcf5033c38ffa7c442f64ff5779dba33f5df31f625/2df1f603ce2f857d962c238a9f9de1e03d528a45280b658918c9a7236dcc885f8076ffecccf12a985af2662623f0523a8f348f00ba74a3b3e30ecdb77c4ff786243dea1228ce47d2641a68b44a48d9f2e875e1bb588812c797877d03/FFU1.pnghttps://www.bcbsri.com/BCBSRIWeb/images/image_popup/skin_type.jpghttps://www.bcbsri.com/BCBSRIWeb/images/image_popup/skin_type.jpg
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    Largest organ in the body

    Represents approximately 16% of total body weight

    An adult has on an average about 18-20 square feet

    (about 2 square meters) of skin

    6 million cells

    5,000 sense end organs

    400 cm nerve fibers

    200 pain sensors

    100 cm blood vessels

    100 sweat glands

    15 sebum glands 12 cold receptors

    5 hairs

    2 heat receptors

    Each Sq.cm of skin is said to have approximately

    Skin : Human integument

    Anatomy

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    Finger and toe nails :

    Hair and hair follicles

    Teeth

    Sebaceous gland, sweat glands,

    apocrine and mammary glands

    Skin : Human integument

    Specialized structures formed by skin

    formed by

    epidermis

    and dermis

    formed by epidermis

    Skin - Dynamic organ - undergoes continuous changes throughout life

    Anatomy

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    Protective barrier interfacing with hostile environment

    - Protects from trauma, UV light, toxins and bacteria Maintains temperature : Thermoregulation

    Gathers sensory information from environment

    Metabolic function: protein & Vitamin D metabolism

    Functions

    Skin - average pH - 5.5 - Acidic

    Acid mantle - amino, lactic & fatty acids in sweat, sebum & hormones

    Acid mantle allows resident protective microflora (bacteria and yeasts)

    & repels pathogenic micro-organisms and reduces body odour

    Skin : Human integument

    Anatomy

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    Immunological surveillance

    Helps restrict fluid loss & preventsexcessive water absorption

    Despite numerous beneficial properties, skin is often abused and

    under-appreciated until its compromise results in pain and loss of

    resistance to infection

    Benjamin C Wood, 2010

    Functions

    Skin : Human integument

    Anatomy

    Immunological surveillance

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    Skin thickness varies - location, gender, age

    Thinnest : eyelid, postauricular

    Thickest : palms and feet

    Male skin thicker than females

    Thin in children starts thickening from 11 years age

    & until 4th-5th decade starts thinning again

    Location

    Gender

    Age

    Benjamin C Wood, 2010

    Skin : Human integument

    Anatomy

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    Epidermis

    Dermis

    Subcutaneous

    Single cell layers of epidermis and dermis start proliferating in the 4th

    week of embryological life

    3 layers of skin

    Anatomy

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    Outer layer of skin : 5% of skin

    Keratinocytes structural cells

    Avascular - gets nutrients and disposes waste

    products by diffusion from underlying dermis through

    basement membrane which separates the 2 layers

    Epidermis Derived from ectoderm

    Anatomy

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    Melanocyte

    Cornified layer (St. Corneum)

    Transitional layer (St. Licidum)

    Granular layer (St. Granulosa)

    Spinous layer

    (St. Spinosa)

    Basal layer

    (St. Basale)

    Malphigian layer

    Basal Lamina

    Melanosomes

    Keratingranules

    Keratin

    Anatomy

    Epidermis

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    Epidermis

    layers

    Characteristics

    Stratum Basale Undifferentiated columnar stem cells.

    Constantly renews epidermal cells

    Stratum Spinosum

    (Malpighian layer)

    Cells change from being columnar to

    polygonal - cells start to synthesize keratin

    Stratum

    Granulosum

    Cells have lost nuclei dark clumps of

    cytoplasmic material -Keratin proteins &

    water-proofing lipids - produced &

    organizedStratum Licidum Only present in thick skin - reduces friction

    & shear forces between str. corneum &

    stratum granulosum

    Stratum Corneum Cells flat - corneocytes. Cells fully mature -

    keratinocytes with keratin protein first

    Anatomy

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    Anatomy

    Melanocyte Langerhans' cell Merkel's cell

    Special cell Function Origin Found in

    Melanocyte Pigment - melanin Neural crest Basal layer, Hair follicles, Retina,Uveal tract & Leptomeninges

    Langerhans Antigen processing Bone marrow Basal, Spinous & Granular layers

    Merkel cell Sense light touch Neural crest Volar aspect of digits, Nail beds,Genitalia and Other areas of skin

    Epidermis Specialized Epidermal Cells : 3 types

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    Junction between epidermis &

    dermis not straight - Finger like

    upward and downward projection

    of dermis and epidermis

    Depth of these inter-digitations vary on the amount onshear force this part of the skin is subjected

    Epidermal and Dermal papillae

    Anatomy

    Dermo - epidermis junction

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    Lying on the surface of epidermis- there are elevations

    & depressions - responsible for

    formation of finger prints in an individual

    Anatomy

    Lamina

    Lucida

    Thinner

    Lies directly beneath basal layer of

    epidermal keratinocytes

    Lamina

    Densa

    Thicker

    In direct contact with underlying dermis

    Dermo-epidermis junction

    Epidermal ridges

    Layers of Dermo-epidermis junction

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    Epidermal appendages - Hair follicles, sebaceous glands, sweat glands,

    apocrine glands - diverticula of epidermis into dermis

    The primary function - sustain & support epidermis

    Papillary layer Reticular layer

    Upper, thinner layer Lower, thicker layer

    Contains capillaries,

    elastic and reticular

    fibers & some

    collagen

    Has collagen, elastic fibers, larger

    blood vessels, closely interlaced

    elastic fibres, coarse collagen

    parallel to surface, sensorystructures, fibroblasts &

    epidermal appendages*

    Anatomy

    Dermis Corium Layer - Derived from mesoderm

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    Found in the dermis it is formed by sebaceous; sweat;

    apocrine and hair follicles

    Important source of epithelial cells with potential for

    division & differentiation

    Re-epithelializes removed or destroyed epithelium :

    eg: partial thickness burns, abrasions, SSG harvest

    In the face, lies in subcutaneous fat - remarkable

    ability of facial skin to repair deep cutaneous wounds

    Collagen - 70% of weight of dermis. Type I (85%) & Type III (15%) of total collagen.

    Elastic fibers constitute < 1% of weight of dermis - but plays enormous functionalrole by resisting deformational forces and returning the skin to its resting shape

    Anatomy

    Epithelial Appendages Intradermal epithelial structures

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    Hair follicle & erector pili muscle

    Sebaceous (oil) & apocrine (scent) glands

    Eccrine (sweat) glands

    Blood vessels & nerves

    Specialized nerve cells

    Meissner's & Vater - Pacini corpuscles

    transmit sensations of touch & pressure

    Anatomy

    Dermis Specialised Dermal Cells

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    Anatomy

    Epidermis,Dermis & Subcutaneous layers of Skin

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    Binds dermis to underlying organs

    Layer of fat & connective tissue

    with larger blood vessels & nerves

    Has areolar & adipose tissue

    Important in thermoregulation

    Size varies throughout body &

    from person to person

    In females - 8% thicker than males

    Subcutaneous layer also referred to as Panniculus Adiposus

    Anatomy

    Subcutaneous tissue : Hypodermis

    Subcutaneous tissue

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    Insulates the body

    Provides protective padding

    Serves as energy storage area

    Houses drainage system of skin

    Anatomy

    Subcutaneous tissue : Hypodermis

    Subcutaneous tissue

    Over developed subcutaneous layer leads to obesity

    Wasting causes skin wrinkling, sagging & premature aging

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    Arise from underlying source vessels each supplies a

    3-dimensional vascular territory from bone to skin -

    Angiosome

    Anatomy

    Blood supply Cutaneous vessels

    Directly from source artery

    (septo/fasciocutaneous perforator)

    From terminal branches of muscular vessel

    (musculocutaneous perforator)

    Emerges from deep fascia & travels toward skin

    - forms extensive subdermal & dermal plexuses

    Originates

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    Dermis - horizontally arranged

    superficial & deep plexuses -

    interconnected by vessels oriented

    perpendicular to skin surfaceCutaneous vessels anastomose with

    other cutaneous vessels form

    continuous vascular network in the

    skin

    Anatomy

    Blood supply Cutaneous vessels

    Convection from cutaneous vessels is a vital component of

    thermoregulation

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    From the subpapillary plexus of small

    arterioles arise an arcade of capillaries

    which loop upwards into each dermalpapilla

    Anatomy

    Blood supply

    Cutaneous vessels

    Venous drainage

    Venous portions of capillary loops empty into postcapillary

    venules of subpapillary plexus empty into larger venules

    - eventually empty into small veins in S/C fat

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    HAS IMPRESSIVE POWERS OF ADAPTATION

    At rest (thermally neutral environment)

    Skin receives 5- 10% of cardiac output

    Can become 50-70% during severe heat stress Zero in a cold environment !

    Vein Capacitance can increase volume by up to 1 liter

    Specialized arteriovenous shunts - glomus bodies

    exist - primarily concerned thermoregulation

    Found most abundantly in dermis of the extremity

    - Skin of hands, feet, nose & ears

    Anatomy

    Skin circulation

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    Cutaneous blood flow : 10-20 times more thanrequired for essential O2 and metabolism

    Large amounts of heat can be exchanged through

    regulation of cutaneous blood flow Cutaneous vessels controlled by hypothalamus

    and autoregulatory mechanisms (endothelium

    & its sensory axon reflex) Controls vasoconstriction & vasodilatation

    Anatomy

    Skin circulation

    Temperature regulation is maintained by having a high-flow arterial

    system combined with a high-capacity, low-linear-velocity venous

    system. This allows maximal heat exchange with the environment.

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    The human adult wound healing process can

    be divided into 3 distinct phases

    Inflammatory phase

    Proliferative phase

    Remodeling phase

    Physiology of wound healing

    Stages of wound healing

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    Within these is a complex and coordinated

    series of events that includes

    - Chemotaxis - Angiogenesis

    - Phagocytosis - Epithelization- Neocollagenesis - New glycosiminoglycans

    - Collagen degradation - Proteoglycans

    - Collagen remodeling

    Results in replacement of normal skin with scar

    Physiology of wound healing

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    Primary

    Delayed primary

    Secondary

    Fourth category : In healing of partial skin

    thickness wounds

    Physiology of wound healing

    Types of wound healing

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    Occurs within hours of repairing a full-

    thickness surgical incision The surgical insult results in the mortality of a

    minimal number of cellular constituents

    Wound heals with minimum scarring

    Physiology of wound healing

    Category 1 : Primary wound healing

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    Wound edges are not reapproximated

    Desired in contaminated wounds

    By fourth day, phagocytosis of contaminated tissuestakes place and process of epithelization,

    collagen deposition & maturation are occurring

    Usually wound is closed surgically at this juncture If "cleansing" of wound is incomplete, chronic

    inflammation ensues - results in prominent scarring

    Physiology of wound healing

    Category 2 : DelayedPrimary wound healing

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    Full-thickness wound allowed to close & heal

    More intense inflammatory response

    Larger quantity of granulomatous tissue is

    fabricated for wound closure

    Pronounced contraction of wounds

    Physiology of wound healing

    Category 3 : Secondary wound healing

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    Involving only epidermis & superficial dermis

    Epithelialization - predominant method of

    healing

    Wound contracture not a common part of

    this process

    Physiology of wound healing

    Category 4: In partial thickness skin wounds

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    Initial phase Hemostasis

    Following vasoconstriction platelets adhere to

    damaged endothelium - discharge ADP, promoting

    thrombocyte clumping - dams the wound

    Alpha granules liberate platelet-derived growth factor

    (PDGF), PF IV & TGF-b

    Fibrinogen cleaved into fibrin - provides structural

    support for cellular constituents of inflammation

    Process starts immediately lasts few days

    Physiology of wound healing

    Events in wound healing

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    Second phase - Inflammation

    Begins in first 6-8 hours

    Leukocytes (PMNs) engorge wound

    TGF-b facilitates PMN migration from surrounding

    blood vessels - "cleanse wound

    Monocytes exude from vessels - called macrophages

    - manufacture various growth factors help in

    multiplication of endothelial cells, sprouting of new

    blood vessels, duplication of smooth muscle cells

    Physiology of wound healing

    Events in wound healing

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    Third phase - Granulation

    This phase consists of different subphases.

    Fibroplasia

    Matrix deposition

    Angiogenesis

    Re-epithelialization

    Fibroblasts lay new collagen of the subtypes I

    and III

    Physiology of wound healing

    Events in wound healing

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    Third phase Granulation

    Wound suffused with GAGs and fibronectin

    contribute to matrix deposition

    Basic FGF & VEGF modulate angiogenesis

    Re-epithelization occurs with the migration of cells

    from the periphery of the wound

    EGF key role in this aspect of wound healing

    These subphases last up to 4 weeks

    Physiology of wound healing

    Events in wound healing

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    Fourth phase - Remodeling

    After 3rd wk wound undergoes constant

    alterations - remodeling - last for years Collagen degraded and deposited in an

    equilibrium-producing fashion

    The collagen deposition in normal wound

    healing reaches a peak by the third week

    Physiology of wound healing

    Events in wound healing

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    Fourth phase Remodeling

    Contraction of wound is an ongoing process from

    proliferation of fibroblasts termed myofibroblasts,

    which resemble contractile smooth muscle cells

    Wound contraction - greater extent with secondary

    healing than with primary healing

    Maximal tensile strength - achieved by 12th week

    Ultimate resultant scar has only 80% of tensile

    strength of original skin that it has replaced

    Physiology of wound healing

    Events in wound healing

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    The definition is often unclear

    Broadest sense - anything that substitutes for

    any of the skin functions eg: being impervious,

    a polyethylene plastic wrap would minimizeevaporation from an open wound - could be

    considered a skin substitute

    A biologic skin substitute, to be more than adressing, should in some way be incorporated

    into the healing wound

    Biological Skin Substitutes

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    The best skin substitute is the skin itself

    Skin grafting is the best procedure has

    limitations and hence the need for substitutes

    Autografts : the patient is the donor

    Allografts or homografts from one individual

    to another within the same species Xenografts or heterografts from one species

    to that of another different species

    Biological Skin Substitutes

    Skin grafts

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    Nontoxic

    Little or no antigenicity

    Immunologically compatible

    Does not transmit disease

    Biologic or Artificial skin substitutes act as a model for the synthesis of

    true dermis or epidermis, thereby reducing the amount of scar tissue

    in the healing wound

    Biological Skin Substitutes

    Ideal Skin substitute

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    Temporary cover - prevents dehydration

    Keeps the wound bed moist (important for

    wound healing) Some skin substitutes stimulate the host

    to produce a variety of cytokines and growth

    factors that promote wound healing

    Biological Skin Substitutes

    Role of Skin substitutes

    More than 20 products commercially available today Auger FA, 2009

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    Grafts of cultured epidermal cells no dermal

    components : Epicel, Vivoderm, Myskin, Cellspray, Cryoskin

    Dermal components alone: Dermagraft, Alloderm, Oasis

    , Biobrane, Matriderm

    Bi-layer substitutes containing both dermal &

    epidermal elements : Integra, Apligraf, Orcel, Permaderm

    Biological Skin Substitutes

    Three categories

    A tool to rapidly cover or even close soft tissue deficits (wounds and

    burns) without the well-described liabilities of donor site morbidity

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    Further categorised

    Acellular

    Cellular

    cellular therapy, tissue engineered products

    Dermal Substitutes

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    Can be permanently incorporated into patients new

    skin layers without being rejected

    They are immediately available

    Avoids risks of cellular allogeneic materials

    Use of thinner STSG reduced donor site morbidity and

    improved incorporation

    Advantages

    Alloderm, Strattice , SurgiMend ,GraftJacket, NeoForm &DermaMatrix - composed of cadaveric dermis - serves as

    a scaffold for the in-growth of recipient tissue

    Dermal Substitutes

    Acellular Dermal allografts

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    Composed of collagen or polymer based

    scaffold that is seeded with fibroblasts from a

    donor cadaver

    Used to cover partial & full thickness wounds

    Must be removed or excised prior to grafting

    full-thickness wounds

    Eg: ICX-SKN, Dermagraft, TransCyte

    Dermal Substitutes

    Cellular Dermal allografts

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    Bilayer products : Eg: Apligraf , Orcel

    Dermal - bovine collagen & neonatal fibroblasts

    Epidermal layer - neonatal keratinocytes

    Allogeneic : cannot be used as permanent skin

    substitutes rejected

    Used in Tx of chronic wounds & donor sites

    Used as overlay dressing on STSG to improve

    function and cosmosis

    Dermal Substitutes

    Composite Dermal allografts

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    Wound closure

    Requires a material to restore the epidermal barrier

    function and become incorporated into the healing

    wound

    Eg: Bilaminate membrane, Transcyte (Dermagraft-TC),

    Cultured allogenic keratinocytes, Apligraf (human skin

    equivalent), Dermograft

    Wound coverage

    Rely on ingrowth of granulation tissue for adhesion

    Eg: Alloderm, Integra, Cultures autologous keratinocytes

    Biological Skin Substitutes

    In chronic wounds : two groups

    l b i

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    Current research in molecular biology, wound

    healing and immunology - likely to yield

    better skin substitutes

    Possible for a synthetic bilayered membrane

    of equal quality to that of skin to be available

    off the shelf for application that is no moredifficult than a change of dressing

    Maurice M Khosh,2008

    Molecular Biology

    Dermal Substitutes

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    THANK YOU FOR YOUR

    KIND ATTENTION